In position sensor applications, electronically commutated DC motors, so-called brushless DC motors, may be used as an alternative to brush-commutated DC motors. These motors generally have higher efficiency and a smaller size for otherwise comparable performance data. However, unlike brush-commutated DC motors, the electronically commutated DC motors must be electronically controlled or commutated, with a relatively accurate knowledge of the rotor position being required to select the control voltages, and knowledge of the motor current being required for torque-based controllers. Inaccuracies when detecting the rotor position and/or when measuring current result in significant reductions in the efficiency and the provided drive torque.
For throttle valve position sensors, it is provided to replace the servomotor by an electronically commutated drive motor, and instead of direct rotor position detection on the motor shaft, to detect the rotor position indirectly based on the already-existing throttle valve angle sensor at the throttle valve, which is connected to the motor shaft via a reducing gear. This system only allows inaccurate rotor position detection with typical uncertainties of more than 10° of the mechanical rotor position.
Furthermore, for reasons of cost, the provision of a current sensor system for detecting the motor current is to be omitted. In the case of such large angle uncertainties and additional parameter fluctuations, a control using commutation patterns which are applied as a function of the detected rotor position results in a violation of the current limits, which may result in the emergency shutdown of the motor by the power electronics.
The object of the present disclosure is therefore to provide a robust control for an electronically commutated position sensor motor, with which an overshooting of the current limits is eliminated, despite inaccuracies which occur during the determination of the rotor position and/or other parameter inaccuracies, and which thereby enables reliable operation.